mirror of
https://github.com/shaka-project/shaka-player.git
synced 2026-06-24 17:35:10 +03:00
Muhammad Haris
54ff2d8f28
This pertains to #2648 (although this is a new feature, not a replacement) and #1404. A CEA-708 decoder that follows the CEA-708-E standard, decodes closed caption data from User Data Registered by Rec. ITU-T T.35 SEI messages, and returns them as cues in Shaka's internal cue format. Furthermore, this pull request fixes and cements some of the logic surrounding CEA-608 and CEA-708 tag parsing on the Dash Manifest Parser. Format: Similar to the CEA-608 decoder, cues are emitted in Shaka's internal format (lib/text/cue.js). This decoder makes use of nested cues. The top level cue is always a blank cue with no text, and each nested cue inside it contains text, as well as a specific style, or linebreak cues to facilitate line breaks. This also allows for inline style (color, italics, underline) changes. Details: - ASCII (G0), Latin-1 (G1), and CEA-708 specific charsets (G2 and G3) all supported. - Underlines, colors, and Italics supported, set as a property on each nested cue. - Positioning of text is supported. (Exception: In CEA-708 the default positioning is left, in this decoder it is centered.) - Positioning of windows not supported, but relevant fields that could be used to support this are extracted and left as a TODO.
121 lines
3.0 KiB
JavaScript
121 lines
3.0 KiB
JavaScript
/*! @license
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* Shaka Player
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* Copyright 2016 Google LLC
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* SPDX-License-Identifier: Apache-2.0
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*/
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goog.provide('shaka.util.MimeUtils');
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/**
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* @summary A set of utility functions for dealing with MIME types.
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*/
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shaka.util.MimeUtils = class {
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/**
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* Takes a MIME type and optional codecs string and produces the full MIME
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* type.
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*
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* @param {string} mimeType
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* @param {string=} codecs
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* @return {string}
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*/
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static getFullType(mimeType, codecs) {
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let fullMimeType = mimeType;
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if (codecs) {
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fullMimeType += '; codecs="' + codecs + '"';
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}
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return fullMimeType;
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}
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/**
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* Takes a Stream object and produces an extended MIME type with information
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* beyond the container and codec type, when available.
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*
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* @param {shaka.extern.Stream} stream
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* @return {string}
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*/
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static getExtendedType(stream) {
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const components = [stream.mimeType];
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const extendedMimeParams = shaka.util.MimeUtils.EXTENDED_MIME_PARAMETERS_;
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extendedMimeParams.forEach((mimeKey, streamKey) => {
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const value = stream[streamKey];
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if (value) {
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components.push(mimeKey + '="' + value + '"');
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}
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});
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return components.join(';');
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}
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/**
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* Split a list of codecs encoded in a string into a list of codecs.
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* @param {string} codecs
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* @return {!Array.<string>}
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*/
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static splitCodecs(codecs) {
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return codecs.split(',');
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}
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/**
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* Get the base codec from a codec string.
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*
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* @param {string} codecString
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* @return {string}
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*/
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static getCodecBase(codecString) {
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const parts = shaka.util.MimeUtils.getCodecParts_(codecString);
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return parts[0];
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}
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/**
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* Get the base and profile of a codec string. Where [0] will be the codec
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* base and [1] will be the profile.
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* @param {string} codecString
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* @return {!Array.<string>}
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* @private
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*/
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static getCodecParts_(codecString) {
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const parts = codecString.split('.');
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const base = parts[0];
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parts.pop();
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const profile = parts.join('.');
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// Make sure that we always return a "base" and "profile".
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return [base, profile];
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}
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};
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/**
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* A map from Stream object keys to MIME type parameters. These should be
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* ignored by platforms that do not recognize them.
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*
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* This initial set of parameters are all recognized by Chromecast.
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*
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* @const {!Map.<string, string>}
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* @private
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*/
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shaka.util.MimeUtils.EXTENDED_MIME_PARAMETERS_ = new Map()
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.set('codecs', 'codecs')
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.set('frameRate', 'framerate') // Ours is camelCase, theirs is lowercase.
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.set('bandwidth', 'bitrate') // They are in the same units: bits/sec.
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.set('width', 'width')
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.set('height', 'height')
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.set('channelsCount', 'channels');
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/**
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* A mimetype created for CEA-608 closed captions.
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* @const {string}
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*/
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shaka.util.MimeUtils.CEA608_CLOSED_CAPTION_MIMETYPE = 'application/cea-608';
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/**
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* A mimetype created for CEA-708 closed captions.
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* @const {string}
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*/
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shaka.util.MimeUtils.CEA708_CLOSED_CAPTION_MIMETYPE = 'application/cea-708';
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